'98 Cadillac DeVille - Rear suspension problems

I would take the car to a shop willing to put it up on a center-post lift and show you exactly what is worn out and needs to be replaced…Get a repair estimate from THEM…This is not rocket science, this is plain nuts and bolts parts replacement…BUT, many of the parts are listed as unavailable…This rear suspension is somewhat unusual in design…Does yours have air springs? That complicates things somewhat…

http://www.gmpartsclub.com/parts-catalog/cadillac/deville/1998/base/4-6l-v8-gas/rear-suspension/suspension-components